The present invention relates to surgically invasive apparatus for accessing a cataracted natural lens via the anterior chamber and a dilated iris, and for removing cataractous material from the lens.
Within the last ten years, there have been important advances in instrumentation and techniques for removal of cataractous-lens material. What has been termed phacoemsulsification is perhaps the most important of these advances, and it should be noted that this term has applied to the use of ultrasonic energy, delivered at the small tip of a piezoelectric or magnetostrictive device; this is the currently favored means of locally fragmenting cataractous tissue, for extraction via a continuous flow of benign liquid. But use of such phacoemulsufication devices calls for great skill, in that excessive delivery or misdirected delivery of ultrasonic energy can result in irreparable damage to the capsulary bag, the retina and/or other parts of the eye.
It has also been proposed, but not generally accepted, to use local delivery of laser radiation to fragment cataractous material, to an extent permitting extraction in a continuous flow of irrigating liquid. But again, there is the prospect of irreversible damage to other parts of the eye, and great surgical skill is required.
To simplify the problem of surgical skill and to reduce the potential for damage through posterior escape of laser radiation, a recently published article* mentions the work of Dr. Patricia E. Bath with her "laserphaco" apparatus, which is said to involve phacoablation, and irrigation and aspiration (I/A). Her apparatus is said to utilize a neodymium-YAG laser (presumably frequency-quadrupled, for ultraviolet-wavelength radiation) or an excimer laser, a laser-phaco probe, a laser-synchronized computer, and a laser interface. The computer is said to sense the high ultraviolet absorbance of the cataracted lens, and the computer selects the correct wavelength; the computer is also said to distinguish between the different refractive indices of the nucleus and the cortex, and to adjust the laser's energy density, thus minimizing the possibility of radiation outside the desired zone. Dr. Bath is quoted as stating that "the computer aims the beam, focuses the beam, tests the beam, and executes ablation of the foci with no escape of radiation posteriorly . . . So what you have coming through a single probe is mapping, focusing, ablation and I/A". FNT "Will Laser Become the Cataract Surgery Instrument of the '90 's?", Ophthalmology Times, Aug. 1, 1990, page 40.
Throughout this case, the terms phacoemulsification, phacoablation, and tissue-fragmentation are deemed to be synonymous, in the sense that they apply to the use of externally supplied and locally delivered energy, whether ultrasonically applied or laser radiation, to break up and reduce cataractous material to a particle size small enough for external removal by the flow of an irrigating liquid in an I/A system.